I'm not an expert but from working with the experts here at Current, I learned that the LEDs which require heat sinks and get hot are higher powered (higher light output) As for the flex strips at the show, they are very low powered which is why they stay very cool.
For a 2 inch hood and high powered, Satellite regular might be your best bet but even then, it isn't that high powered.
You're definitely right about underdriving the LEDs resulting in a cooler fixture as well. This is why our lights run so cool and last so much longer 50,000 hours. Compared to our competitors (marineland's) 17000 hours and hot LED fixture. We use smaller underdriven LEDs to provide better spread. Higher powered, larger LED chips are generally much hotter and focus resulting in deeper penetration. But in the case of planted hobbyists, our tanks rarely get deeper than 24" which is what the Satellite is optimized for. Tanks that are less than 24" deep.